1. Field of the Invention
This invention generally relates to direction finding for transmission signals and, in particular to such apparatuses and methods which receive the transmission signals using a spinning antenna pair.
2. Statement of the Prior Art
The direction finding of transmission signals has been practiced for many year and has been achieved using a wide variety of antenna configurations and signal processing techniques. One such antenna configuration is a circular array of matched antennas which simultaneously receive the transmission signal. The simultaneously received signals from each antenna are processed to determine the relative phase of the received signals between antennas and therefrom determine the direction of origin.
One adaptation of the circular array is a spinning pair of antennas which are repeatedly simultaneously sampled throughout their rotation as a substitute for a full circular array. One of the problems associated with this approach is the spacing of the antenna pair compared to the wavelength of the transmission signal for the purpose of providing a sufficiently large phase measurement for accurate direction determination. This in turn causes a related problem requiring the use of a sufficiently large number of transmission signal samples in order to provide unambiguous phase measurements over the large number of full cycle phase changes during the sampling rotation of the antenna pair.